Question: In the diagram, $\angle PQR = 90^\circ$.  What is the value of $x$?

[asy]
size(100);
draw((0,1)--(0,0)--(1,0));
draw((0,0)--(.9,.47));
draw((0,.1)--(.1,.1)--(.1,0));
label("$P$",(0,1),N); label("$Q$",(0,0),SW); label("$R$",(1,0),E); label("$S$",(.9,.47),NE);

label("$2x^\circ$",(.15,.2)); label("$x^\circ$",(.32,-.02),N);

[/asy]
Since $\angle PQR=90^\circ$, then $2x^\circ+x^\circ=90^\circ$ or $3x=90$ or $x=\boxed{30}$.